so if they were to max out their mod, with 30A & 8.4V, they could achieve 252W. so the min resistance is based on limitation they set on their own, probably based on try and error to see if the actual output have good stabilization, max tolerances etc. is it?

Limitations are based on the components used to supply power, not the math. The math determines the power output, but it's limited either by power ratings or current ratings whichever comes first. It's just how it works with power converters, they can handle a certain amount of power output, but they also have a current limit. It has to do with which components are most heavily loaded under any given condition.

One thing you can get away with in e-cigs is the atomizer is not continuously powered. Limits always come down to heat which is determined by losses. When things are not powered continuously, there's a cooling interval allowing burst outputs. So, if you ensure temperature limits are not exceeded, you can push components pretty far beyond their continuous rating. Plus 50% is a safe assumption.

When using a power converter with a high enough rating, it then comes down to the capability of your power supply. Using two batteries capable of a 30A burst gives you a a maximal power output of 180W using a 6V minimum voltage. So even if you have a 500W/50A converter, the most you could put out would be 180W or 30A, whichever comes first.

In any case, I find these crazy high power outputs pretty impractical. It's possible to set up an atomizer to function well at high outputs like that, but I could never imagine actually vaping with a rig like that all the time. I'd end up on the floor. The vast majority of vapers operate under 25 Watts. Some people are perfectly happy with as little as 5 Watts.

I haven't looked at the specs on that 30A box, but I expect it uses 3 cells in series to get that wide voltage range. It has to be using a buck converter and those usually have a volt or two drop-out. So, minimum input voltage would have to be at least 9V which calls for 3 series cells. That's going to be a big ass box, definitely not something you can put in your pocket. It may be a PWM design, but you still need the higher voltage input to maintain that 2-8V range.

If you want huge power, you could skip the battery altogether and do a passthru. Would be a lot smaller, but then you're tied to a wall plug.

There's a pretty big vaping convention in my town next month I plan to go to (http://www.vaperconwest.com). I think some may scoff at my measly 40W box. But hey, it's small and fits nicely in my pocket. That counts for something.

Funny, when I first did that box I got a couple comments saying why would anyone want that much power. Now it's considered pretty median. I could probably do a 60W booster, I've thought about it and I think it's do-able, but the limited bottom end on the voltage range has always kind of bothered me. The boost only is easier to get big outputs from compared to buck-boost, but I think it's better to stick with a 40W output for a wider voltage range.

At this point in time, I'm doing 7 watts with lots of satisfying taste and big clouds. Call me a wimp but I'm satisfied with it.I will never understand the high wattage vaping. All I get is burnt, hot and nasty tasting juice.

Okay, I bit the bullet and watched the review. I kind of avoid that guy's reviews. They're hard to wade through and there's like zero technical info in them.

Anyway, the battery is a bit of a mystery to me. Says it's 7.4V and there's a 2S charging cable on there which makes me wonder how it's maintaining a range up to 8V. The whole mod is kind of a mystery for me. Sure would like to see the other side of that PCB.

Oh crap, I'm such a dumb-ass. I know all about that mod. I had an involved conversation with the developer when he first started the design probably a year ago on another forum. It's a PWM output. Peak PWM voltage is dependant on battery voltage so it sags as the battery runs down. The most you can get at any one time is battery voltage which is going to range from 6 to 8.4V.

Oh crap, I'm such a dumb-ass. I know all about that mod. I had an involved conversation with the developer when he first started the design probably a year ago on another forum. It's a PWM output. Peak PWM voltage is dependant on battery voltage so it sags as the battery runs down. The most you can get at any one time is battery voltage which is going to range from 6 to 8.4V.

so it is based on buck circuit and self-design? my earlier impression was that it is a box mod using MCU to control for example the OKR or Raptor and display info on OLED.

No, it's a PWM mod. It outputs low frequency PWM. Mods that use that type of regulation typically run the PWM under 50Hz, but I believe that one is somewhat higher, like a couple thousand Hertz. Frequency is not a big factor in terms of atomizer peformance. It's usually run in the sub-audible range to limit the possiblity of audible noise, but there should not be an issue when run higher. For things like motors it matters, but not for an atomizer.

Power is power so it shouldn't matter whether it's delivered with DC or a pulse, but people claim there's a difference. PWM does have some big advantages in that's it's very simple and has very good efficiency. All you need is a switch (MOSFET) and an MCU to control the switch. The downside of PWM is you can not output a voltage higher than input voltage. This is also true for a buck converter, but the difference is a buck converter provides a purely DC output. The disadvantage with PWM is the high peak currents at peak voltages which can be a problem for electrical noise and losses.